Method of temporarily protecting finished coating film on automobile body

ABSTRACT

A releasable aqueous coating composition used for temporarily protecting a finished coating film coated on an automobile body. It contains (A) an aqueous acrylic resin obtained by copolymerizing a monomer mixture of a (meth)acrylic ester monomer as an essential component and other polymerizable unsaturated monomer, except for (meth)acrylonitrile, as an optional component, and having a glass transition temperature of 5° to 30° C. and a weight average molecular weight of 20,000 or more, (B) an ultraviolet light absorber, and (C) a water repellent material. A method of temporarily protecting the finished coating film on the automobile body by coating the releasable aqueous coating composition onto a surface of a finished cured coating film coated onto the automobile body.

FIELD OF THE INVENTION

The present invention relates to a method of protecting a finishedcoating film on an automobile body, which method is useful fortemporarily protecting the finished coating film on the automobile bodywith a releasable aqueous coating composition.

BACKGROUND OF THE INVENTION

It has widely been carried out to temporarily protect a finished coatingfilm on a product, a surface of which has been coat-finished, forexample, a metal product, woodworking product, glass product, plasticproduct, rubber product or the like as in an automobile, vehicle,mechanical part, domestic article or the like.

For example, developments of scuffs on the finished coating film due tocontact with other objects, or of marks, stains, discoloration,pollution and the like due to clouds of sand in air, iron powder, salts,smoking, droppings of birds, humores or carcasses of insects, sunlight,wind and rain, particularly acid rain, and the like during storage in anoutdoor stock yard, or during transportation by cars, railways,trailers, ships and the like in such a period of time as from completionto passing into the possesion of users of these coat-finished products,reduce commercial values of the coat-finished products. In order toprevent the above reduction in commercial values, the finished coatingfilm is temporarily protected during such a period of time as fromcompletion to passing into the possession of users of the coat-finishedproduct. The following methods of temporarily protecting thecoat-finished product are known in the art, all being unsatisfactory.

1 An aliphatic hydrocarbon based solvent dispersion of waxes is coated.An emulsion prepared by dispersing a cleaning agent into a hydrocarbonsolvent or water is used in removing a temporarily coated film. However,the application of the above emulsion to the automobile, for example,results in that anticorrosive agents and anticorrosive waxes coated ontointerior parts of doors and hinge parts are simultaneously removed, too,and further that the use of the solvent may cause smelling of thefinished coating film, and environmental problems such as danger offire, waste water treatment and the like.

2 Such a wax-solid powder organic solvent dispersion is coated that thewax is mixed with the solid powder so that strongth of a wax film may bereduced and a protecting film may easily be removable by hand-wiping.

The above method has such drawbacks that the protecting film shows poorproperties in the temporarily protecting properties, may easily drop bycontact with hands, and may easily be polluted by the acid rain.

3 It is known in the art to use an emulsion containing, as a majorcomponent, acrylic resin as an aqueous, temporarily protecting agent.Since the above emulsions contain carboxyl group-containing monomerssuch as acrylic acid, methacrylic acid and the like in a large amount, aresulting film is difficult to be removed and is removed by use of anaqueous alkaline solution, resulting in needing considerable manhours,and in causing problems of waste water disposal etc.

4 For example, Japanese Patent Application Laid-Open No. 259966/91discloses the use of an acrylic resin emulsion containing(meth)acrylonitrile as an aqueous, temporarily protecting agent, and aresulting film shows excellent properties in film strength and releaseproperties, but has difficulties in waste disposal of a released filmbecause of containing (meth) acrylonitrile. For example, burying of thereleased film may cause water pollution, and incineration of thereleased film may generate hydrogen cyanide gas, resulting atmosphericpollution.

5 For example, U.S. Pat. No. 5,143,949 specification discloses the useof a coating composition containing, as a major component, a vinylacetate emulsion as an aqueous protecting agent, but the resulting filmshows poor properties in acid resistance, water resistance and the like.

As above described, in the case where the temporarily protecting agentis used, it is important to use a composition having the followingproperties.

(a) A resulting film shows a moderate adhesive properties to a finishedcoating film to be protected and is releasable as a continuous sheet byhands or high pressure water stream without damaging the finishedcoating film on releasing.

(b) The composition may be coated by spray coating, roller coating andbrushing.

(c) A resulting film has excellent protecting functions, for example,prevention of stain and pollution due to acid rain, iron powder and thelike, prevention of damages due to contact with other object andchipping, and the like.

(d) A resulting film has moderate properties in elasticity, strength,elongation and durability, and shows poor stickiness.

(e) A resulting film has properties necessary for outdoor storage inwater resistance, weather resistance, and thermal stability.

(f) The composition does not contain additives such as solvent,plasticizer, dispersing agent and the like, which may cause swelling ofthe finished coating film, and defects on the surface of the finishedcoating film, for example, deformation, stain, hazy gloss and the like.

(g) Since a released film is discarded by burying or incineration, thereleased film contains none of any components harmful to human body andenvironment.

For the purpose of solving the above problems 1 to 5 and of developing amethod of temporarily protecting a finished coating film on anautomobile body by use of a releasable aqueous coating compositionhaving above properties (a) to (g), the present inventors made intensivestudies and found out that coating a releasable aqueous coatingcomposition containing a specified acrylic emulsion resin free ofacrylonitrile and ultraviolet light absorber, if needed, under controlof specified viscosity and surface tension onto the finished coatingfilm on the automobile body makes it possible to form a releasable film,which is easily releasable without reducing film strength and elongationeven if exposed to sunlight or the like for a long period of time, whichhas excellent properties in protective functions to acid rain and thelike, and which is free of environmental problems on burying andincineration after releasing, resulting in making it possible totemporarily protect the finished coating film and in accomplishing thepresent invention.

DISCLOSURE OF THE INVENTION

That is, the present invention relates to a method of temporarilyprotecting a finished coating film on an automobile body, which methodcomprises coating a releasable aqueous coating composition containing(A) an aqueous acrylic resin obtained by copolymerizing a monomermixture of a (meth)acrylic ester monomer as an essential component andother polymerizable unsaturated monomer, except for (meth)acrylonitrile,as an optional component, and having a glass transition temperature of5° to 30° C. and a weight average molecular weight of 20,000 or more,and (B) an ultraviolet light absorber onto a surface of a finished curedcoating film coated onto the automobile body.

PREFERRED EMBODIMENTS FOR THE PRACTICE OF THE INVENTION

The finished cured coating film, onto which the releasable aqueouscoating composition is coated, in the present invention may include onesobtained by coating a known curing type coating composition onto theautomobile body, followed by curing under desirable temperature and timeconditions, and preferably may include a coating film having a glasstransition temperature controlled in the range of 50° to 130° C. Thecuring type coating composition may include clear coating compositions,metallic coating compositions containing a metallic pigment such asalminum powder, mica-like powder, mica-like powder coated with titaniumoxide or the like, and, if needed, a color pigment, solid color coatingcompositions containing a color pigment, and the like. Kinds of thecuring type coating composition may include aqueous ones, organicsolvent ones, powder ones and the like. A curing type resin compositionconstituting the curing type coating composition may preferably includeones consisting of a base resin such as acrylic resin, polyester resin,alkyd resin, fluorocarbon resin, silicone resin, epoxy resin or the likeand a crosslinking agent such as amino resin, polyisocyanate compound,polycarboxylic acid compound, polyepoxy compound or the like, polymerscontaining a self-curing monomer such as N-butoxymethyl acrylamide as amonomer component, and the like, acrylic resin based, aminoalkyd resinbased or urethane resin based coating film being particularly preferred.The curing type coating composition may optionally contain extenderpigments, various additives and the like. The above cured coating filmmay include once prepared by coating the above curing type coatingcomposition onto a substrate such as mctal, plastic and inorganicmaterial, directly or, if needed, through a primer, intercoat, basecoator the like, followed by curing under such conditions that the glasstransition temperature of the cured coating film may be within the aboverange.

When the glass transition temperature of the cured coating film is lowerthan 50° C., the releasable film may show poor releasability due to along time outdoor exposure, or film defects such as release mark, stain,hazy gloss and the like may develop on the cured coating film afterreleasing. On the other hand, when the glass transition temperature ofthe cured coating film is higher than 130° C., the releasable film mayspontaneously be released due to its poor adhesive properties duringstorage. The glass transition temperature of the cured coating film isone determined by applying a free cured coating film (wideth 5 mm,length 20 mm, thickness 30 μm) to DYNAMIC VISCOELASTOMETER MODEL VIBRONDDV-II EA, made by TOYO BACDWIN Co., Ltd. for measuring.

The aqueous acrylic resin (A) constituting the releasable aqueouscoating composition used in the present invention is an acrylic resinobtained by copolymerizing a monomer mixture of a (meth)acrylic estermonomer as an essential component and other polymerizable unsaturatedmonomer, except for (meth) acrylonitrile, as an optional component, andhaving a weight average molecular weight of 20,000 or more, a content ofa carboxyl group-containing unsaturated monomer preferably being 5% byweight or less, a glass transition temperature of the acrylic resinpreferably being in the range of 5° to 30° C.

The (meth)acrylic ester may include esterified products between acrylicacid or methacrylic acid and monohydric alcohol having 1 to 28 carbonatoms, for example, methyl acrylate, methyl methacrylate, ethylacrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate,iso-butyl acrylate, iso-butyl methacrylate, tert-butyl acrylate,tert-butyl methacrylate, propyl acrylate, propyl methacrylate, hexylacrylate, hexyl methacrylate, octyl acrylate, octyl methacrylate, laurylacrylate, lauryl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexylmethacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, stearylacrylate, stearyl methacrylate, and the like.

The (meth)acrylic ester may also include hydroxyl group-containingunsaturated monomers such as 2-hydroxyethyl acrylate, 2-hydroxyethylmethacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate andthe like.

The other polymerizable unsaturated monomer may include, except for theabove (meth)acrylic ester and (meth)acrylonitrile, for example, styrene,vinyl toluene, methyl styrene, chlorostyrene, divinyl benzene, vinylacetate, vinyl chloride, vinyl isobutyl ether, methyl vinyl ether,2-ethylhexyl vinyl ether, sulfonic acid group-containing monomer such assulfoethyl methacrylate salt and the like, amide group-containingmonomer such as acrylamide, methacrylamide and the like, and the like.

A mixing ratio between (meth)acrylic ester and other polymerizableunsaturated monomer is not particularly limited, but the (meth)acrylicester is in the range of 1 to 100% by weight, preferably 50 to 99.8% byweight, more preferably 80 to 99.8% by weight, and the otherpolymerizable unsaturated monomer is in the range of 99 to 0% by weight,preferably 50 to 0.02% by weight, more preferably 20 to 0.02% by weightbased on a total amount of both components respectively.

The component (A) may also contain carboxyl group-containing unsaturatedmonomer for copolymerization in an amount of 5% by weight or less,preferably 0.1 to 3% by weight. When the above amount is more than 5% byweight, adhesion to the coating film to be protected may be increased,resulting in making it difficult to release the releasable film.Examples of the carboxyl group-containing unsaturated monomer mayinclude acrylic acid, methacrylic acid, itaconic acid, maleic acid,fumaric acid and the like.

The component (A) may be obtained by subjecting the above monomer in apredetermined amount to emulsion polymerization in the presence of atleast one of emulsifiers such as nonionic surface active agent, anionicsurface active agent, a reactive surface active agent havingcopolymerizable unsaturated group and the like, by use of apolymerization initiator according to the known process in the art. Thecomponent (A) may also be obtained according to the known suspensionpolymerization other than emulsion polymerization.

The resulting acrylic copolymer as the component (A) desirably has aglass transition temperature of 5° to 30° C., preferably 6° to 20° C.When the above temperature is lower than 5° C., adhesiveness of thereleasable film may be increased and strength of the releasable film maybe reduced, resulting in reducing releasability with time. When higherthan 30° C., the releasable film may show poor film-forming properties,and crazing may develop on the releasable film when coated at anenvironmental temperature of 15° to 30° C., resulting in making itimpossible to obtain a continuous film. The component (A) has a weightaverage molecular weight of 20,000 or more, particularly 30,000 to100,000. When less than 20,000, the film strength is reduced, resultingin extremely reducing releasability.

In the case where the acrylic resin (A) only is used, an outdoorexposure of several months or more extremely reduces elongation of thereleasable film due to photo-deterioration, resulting in that thereleasable film may easily be torn to pieces on releasing, and thatconsiderable manpowers may be needed on releasing. Therefore, it is anobject of using the ultraviolet light absorber (B) to prevent the abovephoto-deterioration of the releasable film, and to provide goodreleasability after protection for a long period of time.

The ultraviolet light absorber (B) may include ones known in the art.Specific examples thereof may include salicylic acid derivatives such asphenyl salicylate, p-octylphenyl salicylate, 4-tert-butylphenylsalicylate and the like; benzophenone series such as2,4a-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone,2,2'-dihydroxy-4-methoxybenzophenone,2-hydroxy-a-methoxy-2'-carboxybenzophenone,2-hydroxy-4-methoxy-5-sulfobenzophenone trihydrate,2,2'-dihydroxy-4,4'-dimethoxybenzophenone,2,2'-dihydroxy-4,4'-dimethoxybenzophenone,2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-octadecyloxybenzophenone,sodium 2,2'-dihydroxy-4,4'-dimethoxy-5-sulfobenzophenone,2,2',4,4'-tetrahydroxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone,5-chloro-2-hydroxybenzophenone, resorcinol monobenzoate, 2,4-dibenzoylresorcinol, 4,6-dibenzoyl resorcinol, hydroxydodecylbenzophenone,2,2'-dihydroxy-4(3-methacryloxy-2-hydroxypropoxy)-benzophenone and thelike; benzotriazole series such as2-(2'-hydroxy-5'-methylphenyl)benzotriazole and the like; othercompounds such as oxalic anilide, cyanoacrylate and the like, and thelike.

The ultraviolet light absorber (B) may preferably be used in combinationwith a light stabilizer from the standpoint of releasability with time.The light stabilizer may include ones known in the art, for example,hindered amine based light stabilizers and the like. Specific examplesmay preferably include bis(2,2',6,6'-tetramethyl-4-piperidinyl)-sebacate,4-benzoyloxy-2,2',6,6'-tetramethylpiperidine and the like.Photooxidation of the acrylic resin (A) forms polar groups in a largeamount, resulting in that the releasable film may strongly adhere to thefinished coating film on the automobile body to be unreleasable.Addition of the light stabilizer controls photooxidation to obtain goodreleasability.

Amounts of the component (B) and light stabilizer may optionally beselected depending on objects, but may preferably be in the range of 0.1to 10 parts by weight, particularly 0.3 to 5 parts by weight per 100parts by weight of the component (A) respectively.

The releasable aqueous coating composition used in the present inventioncontains the above components (A) and (B) as the essential components,but may further contain a water repellent material (C) as an optionalcomponent.

Use of the water repellent material in combination with the components(A) and (B) makes it possible to maintain such functions that thereleasable film formed from the above releasable aqueous coatingcomposition has a moderate adhesion onto the surface of the finishedcoating film to be protected, and may completely be releasable withoutdamaging the finished coating film on releasing, for a remarkably longperiod of time, i.e., three to five times longer period of time. Thewater repellent material may preferably include at least one compoundselected from wax series, silicone series, fluorocarbon series and thelike. These compounds may be in the state of being dissolved ordispersed in water, or powdered.

Specific examples of the wax may include vegetable series such ascandelilla wax, carnauba wax, rice wax, Japan wax, jojoba oil and thelike; animal series such as bees wax, lanolin, spermaceli and the like;mineral series such as montan wax, ozocerite, ceresine and the like;petroleum series such as paraffin wax, microcrystalline wax, petrolatumand the like; synthetic hydrocarbon series such as Fischer. Tropsch wax,polyethylene oxide wax, polyethylene wax, acrylic-ethylene copolymer waxand the like; modified wax series such as montan wax derivatives,paraffin wax derivatives, microcrystalline wax derivatives and the like;hydrogenated wax such as hardened castor oil, hardened castor oilderivatives and the like; other waxes such as 12-hydroxystearic acid,stearic amide anhydrous phthalic imide, bisamide, amide, glycerineester, sorbicane ester, C₁₂ or more, preferably C₁₈ or more higheralcohols, C₁₂ or more, preferably C₁₈ or more higher fatty acids, andthe like.

The above wax series desirably have a melting point of about 15° to 250°C., preferably about 20° to 180° C.

When the melting point is outside the above range, the releasable filmmay show poor properties in water resistance, acid resistance and thelike.

The silicone series compounds may include ones having siloxane bond asbackbone, for example, silicone oil, silicone powder, silicone emulsion,silicone water-soluble resin and the like. Specific examples thereof mayinclude dimethyl polysiloxane series, methylphenyl polysiloxane series,cyclic dimethyl polysiloxane series, fluoropolysiloxane series, modifiedones by amino, epoxy, polyether, alcohol, fluoro, mercapto, carboxyl,alkyl higher fatty acids respectively, for example, ones marketed byTORAY DOW CORNING SILICONE Co., Ltd. under the following trade names,silicone oil such as SH203, BY16-828, SF8411, SF8418, BY16-838, SF8422,BY16-848, SH3771, SH3746, SF8419 and FS1265; silicone powder such asR900, R901, R902, F100, F101, F200, F201, F202, F203, F400, F300, F301,F250, E500, E500, E600, E601, E602, E603 and E850; silicone emulsionsuch as SH204, SH490, SH7024, SH7028, SH7036 and SH7060; siliconeaqueous resin such as SH3746, SH3749 and SH3771, and the like. The abovesilicone powder may have a mean particle size of usually about 0.1 to100 μm, preferably about 5 to 50 μm.

Of these, the polyether-modified silicone oil having a molecular weightof 1000 to 20000 and represented by the following formula: ##STR1##where m and n are a positive integer, DOA represents polyether moietydue to ethylene oxide or propylene oxide modification, is the mostprefered in that the polyether-modified silicone oil is hardly solublein water, may easily form a water dispersion by use of a small amount ofsurface active agent, and may sufficiently be oriented in a lower layerportion of the releasable film, resulting in showing excellentproperties in such functions as to lighten an adhesion increase causedin an interface between the finished coating film and the releasablefilm.

The fluorocarbon compound may preferably include ones containingfluoroalkyl group in the molecule and having a molecular weight of about1,000 to 20,000, and may specifically include perfluoroalkylcarboxylate, perfluoroalkyl phosphate, perfluoroalkyl trimethyl ammoniumsalt, pepfluoroalkyl pentanone, perfluoroalkyl ethylene oxide adduct andthe like. Examples of trade names thereof (marketed by Asahi Glass Co.,Ltd.) may include SURFLON S-111, S-112, S-113, S-121, S-131, S-132,S-142, S-145, 131S, 145S and the like.

Of these water repellent agents, the use of wax series and siliconecompound has such advantages that a releasable film having excellentproperties in water resistance and acid resistance may be obtained.

An amount of the water repellent agent (C) used may desirably be in therange of about 0.5 to 30 parts by weight, preferably about 1 to 20 partsby weight of the wax, about 0.01 to 10 parts by weight, preferably 0.1to 5 parts by weight of the silicone compound, and about 0.01 to 5 partsby weight, preferably about 0.01 to 3 parts by weight of thefluorocarbon compound, per 100 parts by weight (as solid content) of theacrylic resin (A).

The releasable aqueous coating composition used in the present inventionmay be prepared by mixing the ultraviolet light absorber (B) and, ifneeded, the water repellent agent (C) as an aqueous emulsion with anaqueous dispersion of the acrylic copolymer (A), or by dispersing theultraviolet light absorber (B) and the water repellent material (C) in apowdered state into the aqueous dispersion of the acrylic copolymer (A).Emulsification of the ultraviolet light absorber and water repellentagent may be carried out by a method of using a mechanical means, amethod of using an emulsifier, or the like.

The releasable aqueous coating composition used in the present inventionmay also contain, if needed, an aqueous dispersion prepared bydispersing a known coating surface adjustor, anti-foaming agent,thickening agent, coloring agent, filler or the like by use of a surfaceactive agent or water soluble resin, and the like. Particularly,incorporation of an aqueous dispersion of titanium white makes itpossible to obtain a whitened releasable film, and the whitening resultsin making it possible to increase a barrier effect against ultravioletlight, heat and the like.

The releasable aqueous coating composition obtained, if needed, as abovein the present invention is desirably coated onto the finished coatingfilm on the automobile body under the control of a viscosity of 0.3 to3.0 Pa·s, preferably 0.7 to 3.0 Pa·s and a surface tension of 40 mN/m orless, preferably 35 mN/m or less. Usually, a surface tension of thefinished coating film surface may be in the range of 25 to 40 mN/m, andparticularly in the case of the roller coating or the like, wettingproperties of the coating composition to the finished coating filmsurface may be important, a surface tension of the protective coatingcomposition may desirably be equal to or less than that of the finishedcoating film surface from the standpoint of obtaining excellent wettingproperties.

When the above viscosity is less than 0.3 Pa·s, the coated compositionmay easily sag. On the other hand, when more than 3.0 Pa·s, theresulting releasable film surface may show poor smoothness and sharpunevenness, and, in the case of roller coating and brushing, troublessuch as poor rotation may be caused, resulting in seriously reducingcoating workability. Control of the above viscosity range may easily becarried out by adding a viscoelasticity selected from sodiumpolyacrylate, acrylic alkyl ester methacrylic acid copolymer,polyacrylic sulfonate, polyether series such as polyoxyalkylene alkylphenyl ether, urethane-modified polyether series, ethylene-bis-aliphaticcarboxylic acid amide, hydroxyethyl cellulose and the like to the abovereleasable aqueous coating composition in an amount of 0.01 to 0.3% byweight based on the above releasable aqueous coating composition.

When the above surface tension is more than 40 mN/m, particularly in thecase of roller coating and brushing, good wetting properties to thefinished coating film on the automobile body may not be obtained, andpoor wetting properties such as cissing make it difficult to form acontinuous releasable film. The above control of the surface tension maybe carried out by adding a polyether-modified silicone oil such asdimethylpolysiloxane modified by ethylene oxide or propylene oxide asexemplified in the above component (C), a fluorocarbon based surfaceactive agent such as perfluoroalkyl carboxylate, perfluoroalkylphosphate, perfluoroalkyl amine oxide or the like, or the like to thereleasable aqueous coating composition in an amount of 0.01 to 0.5% byweight based on the releasable aqueous coating composition.

A method of coating the above coating composition onto the finishedcoating film on the automobile body in the present invention may includeconventionally used coating methods such as brushing, roller coating,spray coating and the like. Of these, the spray coating is the mosteffective, but coating of a limited area only on the automobile body maycause a problem of adhesion of spay mist. Masking of an area other thanthat coated with the protecting coating composition with masking toolsor the like may be possible to prevent the above adhesion problem, butremoving of masking tools may take a long period of time. Therefore,roller coating, particularly pressure feed type roller coating ispreferred in the present invention.

Use of the pressure feed type roller coating machine makes it possibleto coat a necessary area only at nearly 100% coating efficiency and toform a film thick enough to be manually releasable, resulting inproviding a sufficient protecting function, too. A roller cover of theroller to be used may preferably be ones made of an woolen fiber havinga fiber length of 7 mm or more, preferably 12 to 14 mm from thestandpoint of obtaining a suitable film thickness. A fiber length lessthan 7 mm results in making it impossible to obtain a satisfactory filmthickness, making protecting performance unsatisfactory, and reducingreleasability with time. According to the pressure feed type roller,feeding of the releasable aqueous coating composition is carried out byuse of a diaphragm pump, resulting in making possible a continuousfeeding of the releasable aqueous coating composition. A size or lengthof the roller cover may be selected depending on a shape of an area tobe coated on the automobile body.

The coated releasable film may be dried at room temperature for 1 or 2hours, and when heated, for example, at 50° C. for 20 minutes, or at 70°C. for 10 minutes to such a dried state that even exposure to rainimmediately after drying may not cause melting and falling down of thecoated releasable film. Drying also may be carried out by irradiatingmedium infrared rays or far infrared rays for 30 seconds or one minute,followed by heating a surrounding temperature of 50° to 70° C. for 2 to3 minutes to shorten a drying time. Film thickness of the releasablefilm may suitably be in the range of 5 to 100 μm as a dry thickness. Inthe above roller coating, a film thickness of the releasable film maypreferably be in the range of 30 to 100 μm, preferably 50 to 80 μm.

Effect of the Invention

The method of temporarily protecting finished coating film on theautomobile body comprises coating a liquid aqueous coating composition,resulting in being applicable to complicated shapes of the automobilecontrary to a method of applying a protecting sheet in the art and thelike, and in making it possible to greatly reduce manpowers for coatingcompared with manpowers for applying the protecting sheet in the art.

The releasable film formed according to the method of the presentinvention is stable against light, heat and the like, shows excellentreleasability from the finished coating film on the automobile body withtime and shows excellent protecting function against pollution due tosuspended matters and droppings in air, resulting in making it possibleto maintain the commercial values of the finished coating film on theautomobile body for a long period of time, and in making it possible toeasily release the releasable film by hands or high pressure waterstream prior to passing into the possession of users of thecoat-finished automobile. Incineration of the released film does notgenerate any harmful gas such as hydrogen cyanide gas or the likewithout raising any environmental problems.

Industrial Applicability

The method of temporarily protecting the finished coating film on theautomobile body in the present invention is useful for preventingvarious reductions in commercial values concerning the finished, curedcoating film on the coat-finished automobile body, which reductions maybe caused during storage and transportation in a period of time of fromcompletion of coating to passing into the possenssion of users of thecoat-finished automobile.

EXAMPLE

The present invention will be explained more in detail by the followingExamples and Comparative Examples, in which "part" and "%" mean byweight respectively.

(I) Preparation Examples of Acrylic Resin (A) Emulsion

A-1!

A 2-liter four-necked flask equipped with a reflux condenser, stirrer,thermometer and dropping funnel was charged with 312 parts of deionizedwater and 2.3 parts of Newcol 707SF Nippon Nyukazai Co., Ltd., tradename, anionic emulsifier (non-reactive), solid content: 30% by weight!,followed by purging with nitrogen, and keeping at 80° C. Just prior todropping a preemulsion having the following composition, 0.7 part ofammonium persulfate was added, followed by dropping the preemulsion over3 hours.

<Composition of the

    ______________________________________                                        deionized water       350    parts                                            methyl methacrylate   440    parts                                            n-butyl acrylate      352    parts                                            acrylic acid          8      parts                                            Newcol 707SF          53.3   parts                                            Ammonium persulfate   1.5    parts                                            ______________________________________                                    

Thirty mimutes after the completion of the reaction, a solution preparedby dissolving 0.7 part of ammonium persulfate into 7 parts of deionizedwater was added over 30 minutes, followed by keeping at 80° C. for 2hours, lowering the temperature at 20 to 60° C., and controlling pH at 7to 8 with ammonia water to obtain acrylic resin emulsion A-1. Theresulting acrylic resin emulsion was such that the acrylic resin had aglass transition temperature (Tg) of 13.5° C. and a weight averagemolecular weight of about 30,000, and that the emulsion had anon-volatile matter of 51.7%, a viscosity of 0.68 Pa ·s and a meanparticle size of 0.2 μm.

Acrylic resin emulsions A-2! to A-6! were prepared according theformulations with different kinds of vinyl unsaturated monomers as shownin Table 1 in the same manner as in A-1!.

                  TABLE 1                                                         ______________________________________                                        Acrylic resin                                                                 emulsion  A-2      A-3     A-4    A-5   A-6                                   ______________________________________                                        Mono-                                                                         mer                                                                           Compo-                                                                        sition                                                                        methyl    45       42      49     64                                          metha-                                                                        crylate                                                                       n-butyl   32       --      50     26    50                                    acrylate                                                                      ethyl     21       57      --     9     16                                    acrylate                                                                      acryloni  --       --      --     --    33                                    trile                                                                         acrylic                                                                       acid      2        0.5     1      1     1                                     acryla-   --       0.5     --     --    --                                    mide                                                                          Polymerization                                                                          ammonium perfulfate                                                 initiator                                                                     Glass transition                                                                        8.9      19.0    4.3    33.0  -12.8                                 temperature Tg                                                                (°C.)                                                                  Weight average                                                                          40,000   35,000  50,000 45,000                                                                              30,000                                molecular weight                                                              *1 Particle size                                                                        0.20     0.25    0.20   0.20  0.15                                  (μm)                                                                       *2 Non-volatile                                                                         49.7     50.5    51.3   50.2  50.7                                  matter (%)                                                                    *3 Viscosity                                                                            0.43     0.52    0.148  0.26  0.78                                  (20° C. Pa · s)                                               ______________________________________                                    

*1 The particle size means a mean particle size measured by NanosizerN-4 made by COULTER ELECTRONICS INC.

*2 The non-volatile matter means such that a sample was heated at 150°C. for 30 minutes, followed by measuring a residue and calculatingtherefrom.

*3 The viscosity means a value measured at a velocity of 60 rpm by useof a B-type viscometer.

(II) Ultraviolet light absorber (B) was selected from ones in a liquidstate at normal temperature, or ones having a melting point of areaction temperature on preparing the resin or lower.

(III) Preparation of water repellent material (C)

Such ones as impossible to be directly incorporated into the acrylicresin (A) emulsion may be incorporated thereinto after forming anaqueous dispersion by use of a surface active agent as follows.

III-1! Preparation Example of Wax Emulsion

Respective glass vessels were charged with 20 parts of paraffin wax (MP46° C.), montan wax and Hi-Mic-10810 (Trade name, marketed by NipponSairo Co., Ltd., microcrystalline wax) respectively, followed by addingone part of sorbitan monostearate, 3 parts of polyoxyethylene stearylether and 76 parts of water to the above respective vessels, heating at80° to 90° C. with agitation to obtain respective wax emulsions having asolid content of 20%.

III-2! Preparation Example of Silicone Oil Emulsion

To 30 parts of modified silicone oil TSF4445+(Marketed by ToshibaSilicone Co., Ltd., polyether-modified silicone oil) were added 2 partsof polyoxyethylene sorbitan monooleate and 68 parts of water, followedby thoroughly stirring to obtain a silicone oil emulsion having a solidcontent of 30%.

Examples 1-12 and Comparative Examaples 1-11

To respective 100 parts of the above acrylic resin emulsions A-1!to A-6!as solid contents were added the ultraviolet light absorbers and waterrepellent materials in the amounts as solid content as shown in Tables 2and 3, followed by mixing with agitation to obtain releasable aqueouscoating compositions respectively.

To the above compositions, when needed, were added polyoxyalkylenealkylphenyl ether, perfluoroalkylamine oxide, etc., so as to controlviscosity and surface tension as shown in Tables 2 and 3, followed byspray coating the resulting compositions onto the coated panels, a curedcoating film of which has a glass transition temperature of 82° C. and asurface tention of 36.5 mN/m, prepared by coating and curing theaminoalkyd resin coating composition (Marketed by Kansai Paint Co.,Ltd., Trade name: AMILAC) at 140° C. for 30 minutes onto the 0.7 mmthick mild steel sheets surface-treated with PALBOND 3050 (Trade name,zinc phosphate based surface-treating agent, Marketed by NihonParkerrizing Co., Ltd.), followed by drying at 70° C. for 10 minutes toform a releasable coating film having a film thickness of 50 to 70 μmrespectively. Performance test results of the releasable films are shownin Tables 2 and 3.

    TABLE 2                                                                          - Examples                                                                     1 2 3 4 5 6 7 8 9 10 11 12                                                     Formulation                                                                    Acrylic kind A - 1 A - 1 A - 1 A - 1 A - 1 A - 1 A - 1 A - 2 A - 2 A -        3 A - 3 A - 1                                                                   resin amount(part) 100 100 100 100 100 100 100 100 100 100 100 100                  emulsion                                                                  Ultraviolet kind TINUVIN TINVIN TINUVIN TINUVIN TINUVIN TINUVIN               SANDUVOR TINUVIN TINUVIN TINUVIN TINUVIN TINUVIN                                light  1130 1130 1130 1130 1130 1130/LS- 3206 1130 1130 1130/LS- 1130         1130/LS-                                                                        absorber.sup.(                                                                 *.sup.1)       SANOL744    SANOL744  SANOL292             and light           amount(part) 1 1 1 1 1 1/0.5 1 1 1 1/0.5 1 1/0.5                                stabilizer                                                                     Water kind -- paraffin montan micro- TSF4445 TSF4445 TSF4445 -- TSF4445       SH204 SURFLOW TSF4445                                                           repellent   wax wax crysta-       S-112                                        material.sup.(                                                                 *.sup.2)     lline                                             wax                   amount(part) -- 5 3 5 2 2 2 -- 2 2 2 2                                   Viscosity (Pa · s).sup.( *.sup.3) 0.7 0.9 0.7 0.4 1.3 2.0 0.9        0.6 1.0 0.9 0.9 1.8                                                             Surface tension (mN/m).sup.( *.sup.4) 34 30 31 30 26 28 29 35 27 27 26        28                                                                              Film forming properties.sup.( *.sup.5) ◯ ◯            ◯ ◯ ◯ ◯ ◯          ◯ ◯ ◯ ◯ ◯              Roller coating workability.sup.(                                            *.sup.6) ◯ ◯ ◯ ◯              ◯ ◯ ◯ ◯ ◯          ◯ ◯ ◯                                       Releasability                                                                  Initial period.sup.( *.sup.7) ⊚ ⊚               ⊚ ⊚ ⊚ ⊚            ⊚ ⊚ ⊚ ⊚            ⊚ ⊚                                               Heat resistance.sup.(                                                          *.sup.8) ∘ ∘ ⊚ ∘           ⊚ ⊚ ⊚ ∘               ⊚ ∘ ∘ ⊚                   Accelerated weather ∘ ∘ ∘ .smallcirc      le. ∘ ⊚ ∘ ∘ .smallcirc      le. ⊚ ∘ ⊚                             resistance.sup.(                                                               *.sup.9)                                                Accelerate            weather resistance.sup.(                                                        *.sup.10) ∘ ∘ ∘ ∘             ∘ ∘ ∘ ∘ ∘          ∘ ∘ ∘                                       (Coated product appearance changes                                             with time)                                                                     Protecting Properties                                                          Acid resistance.sup.(                                                          *.sup.11) ∘ ∘ ∘ ∘             ∘ ∘ ∘ ∘ ∘          ∘ ∘≠Δ ∘                                    light                                                                          swelling                                                            Iron-powder spreading ∘ ∘ ∘               ∘ ∘ ∘ ∘ ∘          ∘ ∘ ∘ ∘                         properties.sup.(                                                               *.sup.12)                                               Releasable film       combustion test.sup.( *.sup.13) none none none none none none none none        none none none none                                                             (Generation of hydrogen cyanide gas)                                     

                                      TABLE 3                                     __________________________________________________________________________               Comparative Examples                                                          1  2    3    4    5   6    7    8    9    10   11                  __________________________________________________________________________    Formulation                                                                   Acrylic                                                                              kind                                                                              A-1                                                                              A-1  A-1  A-1  A-2 A-2  A-4  A-4  A-5  A-6  A-6                 resin  amount                                                                            100                                                                              100  100  100  100 100  100  100  100  100  100                 emulsion                                                                             (part)                                                                 Ultraviolet                                                                          kind                                                                              -- TINUVIN                                                                            TINUVIN                                                                            TINUVIN                                                                            --  TINUVIN                                                                            --   TINUVIN                                                                            TINUVIN                                                                            TINUVIN                                                                            TINUVIN             light         1130 1130 1130     1130      1130 1130 1130 1130                absorber.sup.( *.sup.1)                                                       and light                                                                            amount                                                                            -- 1    1    1    --  1    --   1    1    1    1                   stabilizer                                                                           (part)                                                                 Water  kind                                                                              -- --   --   TSF4445                                                                            montan                                                                            TSF4445                                                                            TSF4445                                                                            TSF4445                                                                            TSF4445                                                                            --   TSF4445             repellent                                                                            amount                wax                                              material.sup.( *.sup.2)                                                              (part)                                                                            -- --   --   2    3   2    2    2    2    --   2                   Viscosity (Pa · s).sup.( *.sup.3)                                               0.9                                                                              0.2  1.0  3.4  1.2 0.15 0.8  0.9  1.0  0.9  0.9                 Surface tension                                                                          30 30   42   28   27  28   28   27   29   31   28                  (mN/m).sup.( *.sup.4)                                                         Film forming proper-                                                                     ◯                                                                    ◯                                                                      ◯                                                                      ◯                                                                      ◯                                                                     ◯                                                                      ◯                                                                      ◯                                                                      ×                                                                            ◯                                                                      ◯       ties.sup.( *.sup.5)                                                           Roller coating                                                                           ◯                                                                    ×                                                                            ×                                                                            × bad                                                                        ◯                                                                     ×                                      workability.sup.( *.sup.6)                                                                  Sagging                                                                            Poor roller   Sagging                                                    developed                                                                          metting                                                                            rotating developed                                                            conditions                                            Releasability                                                                 Initial period.sup.( *.sup.7)                                                            ⊚                                                                 ⊚                                                                   ⊚                                                                   ⊚                                                                   ⊚                                                                  ⊚                                                                   ⊚                                                                   ◯                                                                      ⊚                                                                   ⊚                                                                   ⊚                                                              1                   Heat resistance.sup.( *.sup.8)                                                           ◯                                                                    ◯                                                                      ◯                                                                      ⊚                                                                   ◯                                                                     ⊚                                                                   Δ                                                                            Δ                                                                            ⊚                                                                   ◯                                                                      ⊚                                                              0                                                         heavy                                                                              heavy                              Accelerated weather                                                                      Δ                                                                          ◯                                                                      ◯                                                                      ◯                                                                      Δ                                                                           ◯                                                                      × un-                                                                        Δ                                                                            ◯                                                                      ◯                                                                      ◯       resistance.sup.( *.sup.9)                                                                brittle           brittle  measured                                                                           heavy                              Accelerate weather                                                                       ◯                                                                    ◯                                                                      ◯                                                                      ◯                                                                      ◯                                                                     ◯                                                                      un-  ◯                                                                      ◯                                                                      ◯                                                                      ◯       resistance.sup.( *.sup.10)            measured                                (Coated product appear-                                                       ance changes with time)                                                       Protecting Properties                                                         Acid resistance.sup.( *.sup.11)                                                          ◯                                                                    ◯                                                                      ◯                                                                      ◯                                                                      ◯                                                                     ◯                                                                      ×                                                                            ×                                                                            ◯                                                                      Δ                                                                            Δ             Iron-powder spreading                                                                    ◯                                                                    ◯                                                                      ◯                                                                      ◯                                                                      ◯                                                                     ◯                                                                      ◯                                                                      ◯                                                                      ◯                                                                      ◯                                                                      ◯       properties.sup.( *.sup.12)                                                    Releasable film                                                                          none                                                                             none none none none                                                                              none none none none gas  gas                 combustion test.sup.( *.sup.13)                      generated                                                                          generated           (Generation of hydrogen                              (6                                                                                 (5 mg/g)            cyanide gas)                                                                  __________________________________________________________________________

(*1) Ultraviolet Light Absorber and Light Stabilizer Ultraviolet LightAbsorber

TINUVIN1130: Marketed by Ciba Geigy A. G., Trade name, Liquid,Benzotriazole derivative ##STR2## SANDUVOR 3206: Marketed by SANDZ,Trade name, Liquid, Ethanediamido-N-(2-ethoxyphenyl)-N'-(4-isododecylphenyl) ##STR3## LightStabilizer SANOL LS-744: Marketed by Sankyo Co., Ltd., Trade name,Powder, 4-benzoyloxy-2,2',6,6'-tetramethylpiperidine

SANOL LS-292: Marketed by Sankyo Co., Ltd., Trade name, represented bythe following formula ##STR4## (*2) Water Repellent Material SH204:Marketed by TORAY DOW CORNING SILICONE Co., Ltd., Trade name, Emulsion,Solid content: 35%. SURFLON-112: Marketed by Asahi Glass Co., Ltd.,Trade name, Perfluoroalkyl phosphate, water/isopropanol solution, solidcontent 15%.

(*3) Viscosity: Viscosity of a coating composition was measured by useof a B-type viscometer of Tokyo Keiki Co., Ltd. The measuring conditionswere such that a coating solution temperature is 20° C. and a rotervelocity is 60 rpm.

(*4) Surface Tension: A surface tension of a coating composition wasmeasured by use of a Kyowa CBVP type tensiometer marketed by KYOWACHEMICAL INDUSTRY Co., Ltd.

(*5) Film-Forming Properties:

Immediately after spray coating to be a dry film thickness of 60 to70μm, a resulting coated test panel was left to stand under theconditions of an environmental temperature of 20° C. and a wind velocityof 0.5 to 0.7 m/S to investigate the coated surface.

◯: Nothing abnormal. A continuous releasable coating film is formed.

Δ: Checking-like abnormality is observed in the range of 30% or less ofthe coated surface.

X: Checking-like abnormality is observed in the range of more than 30%.

(*6) Roller Coating Workability:

The coated panel was coated to be a dry film thickness of 60 to 70 μm bya pressure feed type roller coater and by use of a roller with a rollercover (WOO ROLLER B, Trade name, Marketed by Otsuka Brush ManufacturingCo., Ltd.) having a fiber thickness of 13 mm and a width of 180 mm andmade of an woolen fiber to investigate wetting properties and saggingproperties of the coating compositions and rotating conditions of theroller. (Wetting Properties)

◯: Nothing abnormal. Cissing showing poor wetting properties is notobserved.

Δ: Cissing showing poor wetting properties is observed in the range of50% or less of the surface.

X: Poor wetting properties is shown all over the surface, resulting inmaking it impoossible to form a continuous film.

(Sagging Properties)

Immediately after roller coating, a test panel was kept at an angle ofslope of 60 degree to observe sagging properties.

◯: No sagging is observed.

Δ: Sagging develops in the range of half or less of the width of thecoating.

X: Sagging develops all over the width of the coating.

(Rotating Conditions of Roller)

◯: Nothing abnormal. The roller normally rotates to form a continuousreleasable film.

Δ: Rotating conditions are not so good, and slipping partly takes placeto form a thin film.

X: Rotating conditions are bad, and it is impossible to keeppredetermined film thickness due to slipping.

(*7) Releasability (Initial period):

Formation of a releasable film was followed by leaving to stand at 20°C. for one day, and peeling off the releasable film coated on the testpanel starting from its edge portion at a speed of 1 m/30sec. to examinereleasability.

⊚: Very easily releasable.

◯: Easily releasable.

□: Not so heavy.

Δ: Heavy but releasable.

Δ*: The releasable film is brittle and difficult to be released in theshape of a sheet.

X: Unreleasable.

(*8) Releasability (Heat Resistance):

The test panel was left to stand at 80° C. for 300 hours to examinereleasability in the same manner as in (*7)

(*9) Releasability (Accelerated Weathering Resistance):

In accordance with QUV Accelerated Exposure Test by use of anaccelerated weathering resistance testing machaine, marketed by Q PANELCo., Ltd., testing was carried out under conditions of ultraviolet lightirradiation of 16H/70° C. and water condensation of 8H/50° C. as onecycle for 480 hours (20 cycles), followed by examining releasability inthe same manner as in (*7).

(*10) Accelerated Weathering Resistance (Appearance Changes of FinishedCoating Film)

After peeling off the releasable film as in the above test (*9), thesurface of the aminoalkyd coating film as the finished coating film wasexamined to see abnormalities such as swelling.

◯: Nothing abnormal.

Δ: Light swelling is observed.

X: Serious swelling is observed.

(*11) Protecting Properties (Acid Resistance):

Onto the releasable film was spotted 0.4 ml of 20% sulfuric acid,followed by heating at 60° C. for 15 minutes, washing with water, andpeeling off the releasable film to observe swelling, gloss deteriorationand etching marks on the amino-alkyd coating film.

◯: Nothing abnormal.

Δ: Swelling is observed.

X: Gloss deterioration and etching marks are observed.

(*12) Protecting Properties (Iron Powder Spreading Properties):

Iron powder was sprinkled all over the releasable film through a 200mesh screen, followed by heating at 80° C. for one hour, subjecting to asalt spray test at 35° C. for 48 hours, and peeling off the releasablefilm to examine spreading of the iron powder to the aminoalkyd coatingfilm.

◯: Nothing abnormal.

Δ: Spreading of iron is observed in the range of 30% or less of thecoating film surface.

X: Spreading of iron is observed in the range of more than 30% of thecoating film surface.

(*13) Releasable Film Combustion Test:

Test was carried out in accordance with JIB K7217 as follows to examainegeneration of hydrogen cyanide gas.

Method of generating gas:

Tubular electric oven silica tube process.

    ______________________________________                                        Amount of sample     0.1 g                                                    Temperature          650 ± 10°C                                     Air flow rate        0.5 l/min.                                               ______________________________________                                    

Method of collecting gas:

HCN--Absorption in solution-method of determining an amount of gas:

Pyridine--pyrazolone absorptiometric method

    ______________________________________                                        Limit of detection   0.005 mg/g                                               ______________________________________                                    

What is claimed is:
 1. A method of temporarily protecting a finishedcoating film on an automobile body, which method comprises coating areleasable aqueous coating composition containing (A) an aqueous acrylicresin obtained by copolymerizing a monomer mixture of an acrylic estermonomer or a methacrylic ester monomer as an essential component, acarboxyl group-containing unsaturated monomer and other polymerizableunsaturated monomer, except for acrylonitrile and methacrylonitrile asoptional components, said carboxyl group-containing unsaturated monomerbeing contained in an amount of 5 percent by weight or less in themonomer mixture, and having a glass transition temperature of 5° to 30°C. and a weight average molecular weight of 20,000 or more, (B) 0.1 to10 parts by weight of an ultraviolet light absorber per 100 parts byweight as solid content of acrylic resin (A), and (C) about 0.5 to 30parts by weight of a water repellent material per 100 parts by weight,as solid content of acrylic resin (A), the water repellent materialbeing at least one member selected from the group consisting of waxseries of materials, having a melting point of about 15° to 250° C.,silicone series compounds having siloxane as backbone and fluorocarbonseries compounds onto a surface of a finished cured coating film coatedonto the automobile body to form a releasable coating film, and removingthe releasable coating film after use as a continuous sheet.
 2. Themethod as claimed in claim 1, wherein the releasable aqueous coatingcomposition contains a hindered amine light stabilizer.
 3. The method asclaimed in claim 1, wherein a viscosity of the releasable aqueouscoating composition is controlled in the range of 0.3 to 3.0 Pa·s to becoated.
 4. The method as claimed in claim 1, wherein a surface tensionof the releasable aqueous coating composition is controlled in the rangeof 40 mN/m or less to be coated.
 5. The method as claimed in claim 1,wherein the releasable aqueous coating composition is coated by apressure feed type roller coating machine.
 6. The method as claimed inclaim 1, wherein a glass transition temperature of a finished, curedcoating film coated onto an automobile body is in the range of 50° to130° C.
 7. The method as claimed in claim 1, wherein the finishedcoating film on the automobile body is an acrylic resin based,aminoalkyd resin based or urethane resin based film.
 8. A releasableaqueous coating composition used for temporarily protecting a finishedcoating film coated on an automobile body, and containing (A) an aqueousacrylic resin obtained by copolymerizing a monomer mixture of an acrylicester monomer or a methacrylic ester monomer, as an essential component,a carboxyl group-containing unsaturated monomer and other polymerizableunsaturated monomer, except for methacrylonitrile and acrylonitrile asoptional components, said carboxyl group-containing unsaturated monomerbeing contained in an amount of 5 percent by weight or less in themonomer mixture, and having a glass transition temperature of 5° to 30°C. and a weight average molecular weight of 20,000 or more, (B) 0.1 to10 parts by weight of an ultraviolet light absorber per 100 parts byweight as solid content of acrylic resin (A), and (C) about 0.5 to 30parts by weight of a water repellent material per 100 parts by weight assolid content, of acrylic resin (A), the water repellent material beingat least one member selected from the group consisting of materials waxseries having a melting point of about 15° to 250° C., silicone seriescompounds having siloxane as backbone and fluorocarbon series compounds,a coating film formed by coating the releasable aqueous coatingcomposition being releasable as a continuous sheet upon releasing.
 9. Amethod as claimed in claim 1, wherein the water repellent material (C)is a polyether-modified silicon oil having a molecular weight of 1,000to 20,000 and represented by the following formula: ##STR5## wherein mand n each is a positive integer, and DOA represents polyether moietydue to ethylene oxide or propylene oxide modification.